python 异常 反射

异常 反射

一、异常处理：

 AttributeError 试图访问一个对象没有的树形，比如foo.x，但是foo没有属性x
 IOError 输入/输出异常；基本上是无法打开文件
 ImportError 无法引入模块或包；基本上是路径问题或名称错误
 IndentationError 语法错误（的子类） ；代码没有正确对齐
 IndexError 下标索引超出序列边界，比如当x只有三个元素，却试图访问x[5]
 KeyError 试图访问字典里不存在的键
 KeyboardInterrupt Ctrl+C被按下
 NameError 使用一个还未被赋予对象的变量
 SyntaxError Python代码非法，代码不能编译(个人认为这是语法错误，写错了）
 TypeError 传入对象类型与要求的不符合
 UnboundLocalError 试图访问一个还未被设置的局部变量，基本上是由于另有一个同名的全局变量，
 导致你以为正在访问它
 ValueError 传入一个调用者不期望的值，即使值的类型是正确的

 常用异常

 常用异常

常用异常

 ArithmeticError
 AssertionError
 AttributeError
 BaseException
 BufferError
 BytesWarning
 DeprecationWarning
 EnvironmentError
 EOFError
 Exception
 FloatingPointError
 FutureWarning
 GeneratorExit
 ImportError
 ImportWarning
 IndentationError
 IndexError
 IOError
 KeyboardInterrupt
 KeyError
 LookupError
 MemoryError
 NameError
 NotImplementedError
 OSError
 OverflowError
 PendingDeprecationWarning
 ReferenceError
 RuntimeError
 RuntimeWarning
 StandardError
 StopIteration
 SyntaxError
 SyntaxWarning
 SystemError
 SystemExit
 TabError
 TypeError
 UnboundLocalError
 UnicodeDecodeError
 UnicodeEncodeError
 UnicodeError
 UnicodeTranslateError
 UnicodeWarning
 UserWarning
 ValueError
 Warning
 ZeroDivisionError

 更多异常

 更多异常

更多异常

1  try:
2      intput = raw_input()
3      data = int(intput)
4  except Exception,e:  #e是Exception类的一个对象，调用__str__方法
5  print"请输入数字"

 #输出sb,输出A类的__str__方法

 class A:
     def __str__(self):
         return 'sb'
 obj = A()
 print obj

 #自定义错误异常

 class AlexError(Exception):
     def __init__(self,msg=None):
         self.message = msg
     def __str__(self):
         if self.message:
             return self.message
         else:
             return 'alex error'
 try:
     raise AlexError('error')    #当有值时，输出值，否则输出alex erroer
 except Exception,e:
     print e

 自定义异常

自定义异常

二、反射：

 helpper.py    #模块
 -----------------------------------------------
 def dev():
     return "home dev"
 def index():
     return "home index"

 index.py     #模块
 -----------------------------------------------
 import helpper

 url = raw_input('url:')      #输入helpper/dev

 if url == "helpper/dev":
     ret = helpper.dev()
     print ret
 elif url == "helpper/index":
     ret = helpper.index()
     print ret

 Example

Example

 helpper.py    #模块
 -----------------------------------------------
 def dev():
     return "home dev"
 def index():
     return "home index"

 index.py     #模块
 -----------------------------------------------
 import helpper

 url = raw_input('url:')  #输入helpper/dev
 controller,action = url.split('/')
 func = getattr(helpper,action)
 ret = func()
 print ret

 Example 进阶

Example 进阶

 helpper.py   #模块
 --------------------------------------------
 def dev():
     return "home dev"
 def index():
     return "home index"

 index.py    #模块
 ---------------------------------------------
 controller,action = raw_input("url:").split('/')
 model = __import__(controller)

 func = getattr(model,action)
 ret = func()
 print ret

 __import__和反射 getattr

__import__和反射 getattr

二、反射(2)：

 import sys

 class WebServer(object):
     def __init__(self,host,port):
         self.host = host
         self.port = port
     def start(self):
         print("Server is starting...")
     def stop(self):
         print("Server is stopping...")
     def restart(self):
         self.stop()
         self.start()
 if __name__ == "__main__":
     obj = WebServer('localhost','')
     if sys.argv[1] == "start":
         obj.start()

 example

example

 import sys

 class WebServer(object):
     def __init__(self,host,port):
         self.host = host
         self.port = port
     def start(self):
         print("Server is starting...")
     def stop(self):
         print("Server is stopping...")
     def restart(self):
         self.stop()
         self.start()
 if __name__ == "__main__":
     obj = WebServer('localhost','')
     cmd_list = {
         'start':obj.start,
         'stop':obj.stop
     }
     if sys.argv[1] in cmd_list:
         cmd_list[sys.argv[1]]()

 example 字典形式

example 字典形式

 import sys

 class WebServer(object):
     def __init__(self,host,port):
         self.host = host
         self.port = port
     def start(self):
         print("Server is starting...")
     def stop(self):
         print("Server is stopping...")
     def restart(self):
         self.stop()
         self.start()
 if __name__ == "__main__":
     obj = WebServer('localhost','')
     if hasattr(obj,sys.argv[1]):
         func = getattr(obj,sys.argv[1])  #获取obj.start 的内存地址
         func()

 example 进阶hasattr  getattr

example 进阶hasattr getattr

 import sys

 class WebServer(object):
     def __init__(self,host,port):
         self.host = host
         self.port = port
     def start(self):
         print("Server is starting...")
     def stop(self):
         print("Server is stopping...")
     def restart(self):
         self.stop()
         self.start()

 def test_run(name):
     print("running..",name)

 if __name__ == "__main__":
     obj = WebServer('localhost','')
     if hasattr(obj,sys.argv[1]):
         func = getattr(obj,sys.argv[1])  #获取obj.start 的内存地址
         func()
     setattr(obj,"run",test_run)
     obj.run('xxx')

 ----------------------------------------------------------------------

 #/usr/bin/env python
 # -*- coding:utf-8 -*-

 import sys

 class WebServer(object):
     def __init__(self,host,port):
         self.host = host
         self.port = port
     def start(self):
         print("Server is starting...")
     def stop(self):
         print("Server is stopping...")
     def restart(self):
         self.stop()
         self.start()

 def test_run(self,name):
     print("running..",name,self.host)

 if __name__ == "__main__":
     obj = WebServer('localhost','')
     if hasattr(obj,sys.argv[1]):
         func = getattr(obj,sys.argv[1])  #获取obj.start 的内存地址
         func()
     setattr(obj,"run",test_run)
     obj.run(obj,'xxx')

 setattr

setattr

三、设计模式：

 class SqlHelper:

     __static_instance = None

     def __init__(self):
         self.hostname = '0.0.0.0'
         self.port = 3306
         self.user = 'root'
         self.passd = ''

     @classmethod
     def instance(cls):
         if cls.__static_instance:
             return cls.__static_instance
         else:
             cls.__static_instance = SqlHelper()
             return cls.__static_instance

     def fetch(self):
         pass
     def remove(self):
         pass

 def add_user():
     obj = SqlHelper.instance()
     obj.fetch()

 def del_user():
     obj = SqlHelper.instance()
     obj.remove()

 print id(SqlHelper.instance())
 print id(SqlHelper.instance())

 单例模式一

单例模式一